Female head lice lay their eggs, called nits, on human heads, cementing them onto hairs with a glue-like substance. Most head lice eggs hatch in about 1 week.
Freshly hatched nymphs must find a blood meal within 24 hours. Nymphs mature after three molts, which takes about 7 days after hatching.
Females can reproduce when they are about 10 days old. Adult lice live for 3 to 5 weeks.
Head lice complete their entire life cycles on their human hosts. Head lice who fall off of their hosts die of desiccation or starvation within 2 days.
Nymphs and adult head lice typically feed several times a day. An adult female can lay up to 150 nits in her lifetime.